SEISMIC CRUSTAL STRUCTURE OF THE NORTH CHINA CRATON AND SURROUNDING AREA: SYNTHESIS AND ANALYSIS

We present a new digital model (NCcrust) of seismic crustal structure of the Neoarchean North China Craton and its surrounding orogeny belts. All available seismic profiles, complemented by receiver function interpretations of crustal thickness, were used to establish the four layer (sedimentary cover, upper crust, middle crust and lower crust) model. The NCcrust, defined on a 0.25° × 0.25° grid, includes Moho depth, internal structure of the crust and the Pn velocity in the study area. The crust is thin (30-32 km) to the east of the 120° E meridian, much thinner than the global average for cratonic crust. The average Moho depth of the western part is 38-44 km. The Moho depth of the Sulu-Dabie-Qiling-Qilian orogenic belt ranges from 31 km to 51 km. The sedimentary cover is 2-5 km thick in most of the region and typical thicknesses of the upper, middle, and lower crust are 16-24 km, 6-24 km, and 0-6 km, respectively. The crystalline crust has average P-wave velocity ranging from 6.28 km/s in the northeastern and the central southern parts of the craton to 6.42 km/s in the western part with the thicker crust, which includes a lower crustal layer (north Ordos Basin). The velocity in the uppermost mantle is very heterogeneous with Pn values ranging from 7.8 km/s (along the Tanlu Fault) to 8.3 km/s (the Ordos Basin). We examine correlations between the Moho depth and topography for 7 tectonic provinces in the North China Craton and speculate on mechanisms of isostatic compensation.